I like pretty much all sports, both as participant and spectator. The American "big 3" (baseball, basketball, football) are OK but I gravitate toward more obscure sports like badminton and curling.

Here are some sports that you not be familiar with:

• Real tennis. I've actually played this, at the Queen's Club in London, with Francois Grey. The rules are extremely complex; a partial explanation is here.
• Bo-Taoshi. See for yourself. Note: once I was in Tokyo and my hotel room overlooked a school playground. I observed a number of games, and they all rewarded teamwork rather than individual achievement. For example, a pair of long wooden skis that 10 or so kids strapped their feet into - to move forward, everyone had to act in unison.
• Kabaddi. A much fancier version of tag. Also beach Kabaddi.
• Dodgeball. Another children's game played by adults.
• Cornhole. A picnic game played by mouth-breathers.
• Team handball. A game in the hockey mold, like lacrosse.
• Teqball. Ping-pong played with soccer skills.
• Sepak Takraw Badminton with hockey skills. Amazing. Intro video.
• Netball. A basketball variant. Rules. Similar to the Dutch game of Korfball.
• Bossaball. Volleyball on trampolines and bouncy castles.
• SlamBall. Basketball on trampolines.
• Cycle Ball. Hockey on bicycles.
• Unicycle basketball. This is played in a park near my house. The name says it all. There are unicycle variants of other sports too.